Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, video and the like, and deployments are likely to increase with introduction of new data oriented systems such as Long Term Evolution (LTE) systems. Wireless communications systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems and other orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals (also know as user equipments (UEs), or access terminals (ATs). Each terminal communicates with one or more base stations (also know as access points (APs), Node Bs, Enhanced Node Bs (EnodeBs), or eNBs) via transmissions on forward and reverse links. The forward link (also referred to as a downlink or DL) refers to the communication link from the base stations to the terminals, and the reverse link (also referred to as an uplink or UL) refers to the communication link from the terminals to the base stations. These communication links may be established via a single-input-single-output (SIMO), single-input-multiple output (SIMO), multiple-input-single-output (MISO), or multiple-input-multiple-output (MIMO) system.
One desired goal in wireless communication systems such as LTE systems is reduction of user plane latency. One way of achieving this is to reduce uplink latency by allowing contention-based uplink transmissions. Contention-based uplink transmissions are transmissions where multiple user devices transmit data packets over a common or shared channel resource. This approach can reduce delay when an offered load is not too large. Moreover, this approach may also allow savings on uplink control channel resources.
Contention-based protocols that can provide significantly higher data throughput compared to the Aloha protocol have been proposed. These approaches seek to control uplink arrival rates such that the ratio of total received power to background noise can be kept below a tolerable level.